We show that aqueous sodium sulfate solutions exhibit an unrealistically large degree of
ion pairing and clustering when modeled using non-polarizable force fields, with clusters resembling
precipitate readily forming in a 0.5 m solution at ambient conditions. This aggregation
behavior was found to be persistent in non-polarizable water for a range of parameters
of the sulfate anion. In contrast, a polarizable potential performs satisfactorily, producing a
well dissolved salt with a degree of association that is consistent with activity data for real
solutions. Most of this improvement is due to polarization of water molecules in the vicinity
of the divalent sulfate anion, which enhances its solvation.